1. Field of the Invention
The present invention relates to a method for preventing freezing of the chilled water in a water cooled chiller within an HVAC system. The invention also relates to a system for preventing freezing of the chilled water in a water cooled chiller.
2. Background of the Invention
It is often necessary to operate water cooled chillers at temperatures within a few degrees of the freezing point of water. As is known, the water in the chiller is cooled in a heat exchanger where the water is cooled by a refrigerant that accepts heat from the water in an evaporator. In existing water chillers, the control system is often programmed to shut down the water chiller as soon as the evaporator temperature decreases to a certain temperature below freezing. The shutdown may occur even though this temperature drop would only be temporary and would not result in freezing of the water in the water chiller. These transient temperature drops are often due to system disturbances caused by varying building loads, start-up, or any number of other reasons. These shutdowns are often unnecessary because the water inside the tubes will not freeze immediately.